The only limit on how many protocols you can decode in one capture is the number of channels on the device. There is no software limit to how many analyzers you can add, or how many instances of a particular type of analyzer you can add.
For instance, it's very common to use two instances of the async serial analyzer, one to decode TX, and one for RX.
trello ID: 56c77d71eb472a8d4dbb3877
trello data: 977772680